This invention relates to an apparatus for producing an unidirectional force of a type comprising a rotary body on which are mounted masses which can move relative to the body so as to change the position of their centre of gravity relative to an axis of rotation of the rotary body with the movement of the centres of gravity being arranged to cause a unidirectional force in a direction transverse to the axis of rotation.
Various designs for devices of this type have been proposed and examples are shown in U.S. Pat. Nos. 3,807,244 (Estrade), and 4,095,460 (Cuff) and also in European patent application publication No. 128008 (Thornson). The designs however proposed in these arrangements have a number of disadvantage including the complexity of the design, the necessity for accurate balancing, the use of various gear drive arrangements, and in some cases the inability to control the direction of force.
It is one object of the present invention, therefore, to provide a device of this general type which has a simple and effective design enabling generation of a unidirectional force. According to the invention, therefore, there is provided an apparatus for producing a unidirectional force comprising a body symetrical about a central axis thereof, means mounting the body for rotation about said central axis, drive means for driving said rotation of said body, a plurality of pendulum masses, means mounting each mass on said body of said central axes with said pivot axis spaced angularly around said central axis such that said body and said masses can rotate in a balanced condition around said central axis with said masses tending to move to an extended position in which a centre of gravity of each mass lies on a line joining said central axis and said respective pivot axis, a cam surface arranged to extend around said central axis, means on each of said masses for engaging on and running around said cam surface such that when engaged therewith each mass is pivoted out of said extended position to a retracted position in which said centre of gravity is moved radially inwardly, said cam surface having an angular extent less than 360.degree. so as to provide an angular part of the rotation of the body in which the masses are free to move toward the extended position, and spring means for engaging each of said masses as it moves to the extended position and arranged to provide a spring restraining bias force acting to return said mass to said retracted position.
Preferably the device uses a direct drive motor acting upon the rotary body so as to avoid the necessity for gears and other drive interconnections which add to complexity and cost.
Preferably the device is mounted in a housing which can be adjusted in two directions in order to adjust the direction of the unidirectional force.
Preferably the spring means controlling the movement of the pendulum masses comprises a plurality of separate leaf springs each associated with a respective one of the pendulum masses for engaging that mass as it moves to the extended position and for providing a biasing force tending to return it to the retracted position.